If the bubbles are between the NV and the Carb, but NOT between the tank and the NV then there is an air leak at the NV or in the line from the NV to the carb (It could be a pinhole that is too small to see, so replace the line since it is the easiest thing to do)

If the bubbles start before the NV, there is either an air leak in the plumbing or you're getting fuel foaming.

If you replaced the entire NV assembly with one from a 61 you will be ok, but if you only replaced the needle itself, that may be a problem.